Thread arrangement for earth boring members

ABSTRACT

A thread arrangement for connecting solid, or essentially solid shafts, as well as shafts having a longitudinal bore extending therethrough for use in earth boring operations, which thread arrangement is defined in terms of the geometry, including the diameters, of the shafts upon which the thread is employed, rather than in specific, or absolute, unchangeable dimensions.

United States Patent l l l I lnvcntors Howard 1. Lorenz;

Kess M. Verheul, both of P. 0. Box 9582, Houston, Tex. 77011 Appl. No.790,699

Filed Jan. 13, 1969 Patented June 22, 1971 THREAD ARRANGEMENT FOR EARTHBORIN MEMBERS 14 Claims, 7 Drawing Figs.

US. Cl 285/334, 285/390 Int. Cl F16] 25/00 Field of Search 285/333,

[56] References Cited UNITED STATES PATENTS 2,l96,966 4/1940 Hammer285/390 X 3,129,963 4/1964 Robbins 285/334 3,355,192 11/1967 Kloesel etal. 285/334 X 3,388,752 6/1968 Hanes et al, 28,5/334 X PrimaryExaminer-Dave W. Arola Attorney-Hayden & Bee

ABSTRACT: A thread arrangement for connecting solid, or essentiallysolid shafts, as well as shafts having a longitudinal bore extendingtherethrough for use in earth boring operations, which threadarrangement is defined in terms of the geometry, including thediameters, of the shafts upon which the thread is employed, rather thanin specific, or absolute, unchangeable dimensions.

mi 2 f llllll MAKE UP TORQUE (/000 F7.

PATENTED JUN22 I971 SHEET 2 BF 3 I LUBE/CA r50 I AND 0077-) l m /0 20 J040 av BREAK 01/7 ra/wuz (/000 f7. 15;. M PWJ TYPICAL FOR Howard f.lower/z Keen; M Verfieu/ INVENTORS PATENTEDJUNZZHYI f 3,586,353

' sum 3 or 3 I Howard lore/22 flee: M l erfieu/ INVENTORI and? nauelWiIArm a ewA THREAD ARRANGEMENT FOR EARTH BORING MEMBERS BACKGROUND OFthe INVENTION shafts upon which the thread is employed as opposed toabsolute, unchangeable dimensions without regard to shaft geometry.

2 Description of the Prior Art Applicants are aware of the patent to DB.Robbins, US Pat. No. 3,129,963 wherein a thread arrangement is shown forthe pin and box of tubular members. In the Robbins patent the mating pinand box are described as having substantially complementary cooperatingtapered surfaces on the flanks of the threads which are shown andunderstood to contact so that both flanks of each thread are loadedafter make up. Also, the threaded complementary cooperating threadedsurfaces on the male and female members are tapered approximately 7 to9from the longitudinal axis of the cylindrical members.

In the US. Pat. No. 3,355,192 to J.A. Kloesel, Jr. et al. it iscontemplated that the threaded connections on the members are made uponly hand tight and that applied torque during drilling makes 'up thethreaded connections between the pin and box more fully.

Unfortunately, the thread contours of the prior art are such that theymay cause excessive stress in the pins and boxes when they are connectedtogether and possibly even splitting of the boxes and breaking off ofthe pins when high tensile loads as well as high rotational torques areapplied thereto.

Also, in some instances, the pin and box of prior art threadedconnections does not make-up to a predetermined make-up torque or to apredetermined level of torque so that the joint will not become loosenedduring use. On the other hand, some of the prior art teaches that it ispreferable to make-up the connections only hand tight and let the jointtighten an unknown amount as it rotates. Also, in earth boringoperations it is not always possible or economical to prevent dirt,sand, mud and particles of rock which are normally present during theearth boring operations and during the making of a connection or joiningof sections of shaft together in earth boring operations from becomingcaught or clogged between the pin and box as they are threadedlyconnected together. This foreign matter between the threaded portions onthe pin and box sets up additional stresses within the pin and boxduring make-up and use of the shafts.

Additionally, with some prior art thread configurations it is impossibleto predict the torque level necessary at which the shafts may bedisconnected at the pins and boxes and thus it may, in somecircumstances, be difficult if not impossible to determine therequirements of the tools necessary to disconnect the pin and box.Similarly in some situations where the amount of torque required ornecessary to disconnect or break out the pin and box is unknown, it isalso unknown as to whether the capability of the tools employed to breakout the joints might be exceeded.

Another disadvantage with some of the threaded arrangements of the priorart is that the threaded a of the prior art is that the threadedarrangement on the pins and boxes of the shafts is not provided withcooperating unthreaded surfaces to aid in guiding the pin and box intoinitial thread contact as the pin and box are stabbed together, as wellas aiding in transmitting high tensile and compressive loads, as well aslarge rotational forces and reverse bending moments after the pin andbox are threadedly engaged.

Another disadvantage with some of the threaded arrange ments with theprior art is that the thread configuration is empirically andunchangeably defined and predetermined without regard to some of thecharacteristics of the shafts employed, such as the outer diameter ofthe shaft or tubular member in which they are to be employed, whether ornot the shaft is solid or has a longitudinal bore extendingtherethrough.

SUMMARY OF THE INVENTION The present invention provides a threadconfiguration for the pins and boxes of solid, or essentially solidshafts as well as shafts having a longitudinal bore extendingtherethrough for use in earth boring operations wherein the threadarrangement on the pin and box is related to various characteristics ofthe shaft such as the outer diameter of the shaft on which it is to beemployed as well as to the inner diameter of any bore which may extendlongitudinally therethrough, rather than being unchangeably fixed atsome predetermined value.

Another object of the present invention is to provide a threadconfiguration for the pins and boxes of solid or essentially solidshafts as well as shafts having a longitudinal bore extendingtherethrough which is essentially unaffected by dirt, sand, mud andparticles of rock which may be encountered during making the connectionof joints in earth boring operations. Similarly, the threadconfiguration of the present invention renders the relationship ofmakeup torque to breakout torque virtually unaffected by variations inwhether or not the pins and boxes are clean, or whether or not they arelubricated or nonlubricated.

Still another object of the present invention is to provide a threadarrangement for the pins and boxes of solid or essentially solid shafts,as well as shafts having a longitudinal bore extending therethrough foruse in earth boring operations which thread arrangement is provided witha thread contour that tends to reduce the splitting of the boxes and thebreaking off of pins caused by stress raising contours of other threadforms of the prior art.

Yet a further object of the present invention is to provide a threadconfiguration which reduces the tendency of boxes to split or thetendency of pins to break off caused by the pressure of foreign matterbetween the threads on pins and boxes thread during makeup and use, orthe lack of adequate shoulder pre-load during makeup of the connectionas a result of foreign matter between threads. In the present inventionthe thread arrangement for shafts is such that the shafts may beconnected together in shoulder to shoulder abutment to preventadditional makeup during rotation of the shafts.

Additionally, the thread arrangement of the present invention is suchthat a consistent relationship between the amount of torque required toconnect the thread arrangement on pins and boxes together and the amountof torque required to disengage pins and boxes is maintained,substantially regardless of foreign matter in the box or ,on the pin atthe time that they are initially stabbed together and threadedlyconnected.

Yet a further object of the present invention is to provide a stabbingnose on the pin of a shaft in cooperation with a thread arrangement onpins and boxes of shafts to enable the pins and boxes to be more readilystabbed together and the threads initially contacted for subsequentthreaded engagement to a predetermined amount of torque to inhibitsubsequent relative rotation between the pins and boxes or additionalmakeup between the pin and box during use.

Still another object of the present invention is to provide a threadconfiguration on the pins and boxes of solid, or essentially solidshafts, as well as shafts having a longitudinal bore therethrough havingcertain parameters related to the outer diameter of the shaft, the innerdiameter of any longitudinal bore extending through the shaft and otherparameters as set forth in detail in the specification, so that thethread size will vary in relation to the outer diameter of the shaft, aswell as the diameter of any bore therethrough.

Still another object of the present invention is to provide a threadarrangement for the pin and box of solid, or essentially solid shafts,as well as shafts having a longitudinal bore therethrough wherein thethread crests on the pin and box have a desired length, and the roots ofthe threads on the pin and box are formed on a radius which is tangentto the thread flanks that the roots join together, with one thread flankbeing substantially longer and inclined more relative to thelongitudinal axis of the shaft than the outer thread flank. The threadedarrangement is positioned on the pin and box between unthreaded portionsthereon, with the unthreaded portions thereon, with the unthreadedportions on the pin being cylindrical, and one of which is to assist instabbing two tubular members together and aid in maintaining rigiditywhen the members are threadedly engaged.

Still another object of the present invention is to provide a threadedarrangement for the pins and boxes of solid, or essentially solidshafts, as well as shafts having an internal bore therethrough for usein earth boring operations which is substantially unaffected by dirt,sand, mud or rock particles which are normally present during making theconnection of joints in earth boring operations. The thread arrangementis contoured to reduce stresses that might occur in other threadarrangements and it will also transmit extremely high rotational torquesin combination with extremely high compressive and tensile loads arisingfrom imposed input power, shaft weight and alternating stressesresulting from high reverse bending moment.

The present invention is applicable in earth boring operations whereinthe threaded connection between joints may be subjected to 2 millionpounds, or even greater, if necessary, tensile loading and rotationalforces, or torque to 300,000 or even greater, if necessary, foot pounds.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a sectional view of a boxformed in accordance with the present invention in a shaft having a boretherethrough, with the pin on an adjacent shaft being shown in elevationand stabbed in misalignment relative to the box;

FIG. 2 is a sectional view illustrating the pin and box of the presentinvention in final madeup position with the shoulder on the box in firmcontact with a shoulder formed on the pin;

FIG. 3 is a diagrammatic representation of the threaded arrangement ofthe present invention on a pin of a shaft with nomenclature thereonrelated to the threaded configuration;

FIG. 4 is a graph illustrating the relationship of makeup torque tobreakout torque with the threaded arrangement of the present inventionwhen employed under various conditions;

FIG. 5 illustrates the thread configurations of the present invention ona tubular member having pin ends;

FIG. 6 illustrates the thread configuration of the present invention ona tubular member having box ends; and

FIG. 7 illustrates a partial sectional view of the thread configurationon a larger diameter member than that illustrated in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Attention is first directed toFIG. 1 of the drawings wherein Y the thread configuration of the presentinvention is referred to generally by the numeral 10. As describedherein the shaft 11 and the shaft 12 shown in FIG. 2 are provided withinternal bores 11a and 12a extending longitudinally thereofrespectively; however, it is to be understood that the threadconfiguration of the present invention can be used on the pin and box ofsolid, or essentially solid shafts for connecting sections or lengths ofshafts together, and that the illustration in FIGS. 1 and 2 employingthe bores 11a and 12a longitudinally of the members 11 and 12 is forpurposes of illustration only.

It can also be appreciated that the invention will be described indetail wherein a pin referred to generally by the letter P is providedon one end of a shaft 12 and a box designated generally by the letter Bis provided on the other end of a shaft whereby adjacent joints orsections of shafts may be threadedly engaged by engaging the pin P onone shaft with the box B on the next adjacent shaft as will be describedin greater detail hereinafter. However, the invention can be as readilyemployed on shafts or tubular members having two pin ends, or two boxends as shown in FIGS. 5 and 6.

Referring to FIGS. 1, 2 and 3, the threaded arrangement on the pin P isdefined by an annular shoulder 15 extends radially inwardly from theouter periphery l6 and terminates at the juncture with the cylindricalneck 18 which is on a smaller diameter than the outer diameter or outerperiphery of the shaft. At the juncture of the cylindrical neck 18 andthe shoulder 15 a curved surface 19 is formed and from the curvedsurface the cylindrical neck 18 extends longitudinally towards thethreaded portion referred to generally by the numeral 20.

The threaded portion 20 on the pin P extends longitudinally from thecylindrical neck and the end threads thereon t erminate in a manner wellknown in the art to define the beginning and termination of the threadedarea or portion 20. Shown in FIG. 2 in solid line and extendinglongitudinally from the threaded portion 20 on the pin P is anunthreaded cylindrical nose 21 which extends to the end 22 of the shaft.The dotted line 60 represents the construction when the nose 21 iseliminated, as it may be in some situations.

The box B on each of these shafts is provided with an unthreaded portion23 adjacent the outer end 25 of the box B which extends inwardlytherefrom to the threaded portion referred to generally by the numeral26. As with the pin P the threads on the box B are started andterminated in a manner well known in the art, and at the end of thethreaded portion 26 on the box B, there is an unthreaded portion 28which is recessed and extends longitudinally of the box B at the innerend thereof.

Generally speaking, in the type earth boring operations to which thepresent invention is directed, the box 8 will be stabbed downwardly overthe pin P as illustrated in FIG. 1 of the drawings; however the presentinvention also may be used in situations where the pin is stabbed in thebox. FIG. 1 illustrates the extreme or greatest misalignment that mightoccur during stabbing operations of a box B on a pin P and it can benoted that the unthreaded nose 21 abuts the last thread as representedat the numeral 30 and the threaded portion 20 on the pin P is engagedwith one of the threads of the box B as represented at 32 in FIG. 1 sothat upon relative rotation the box B and pin P are aligned andthereafter the threaded portions 20 and 26 on the pin P and box Bengaged until the outer end or shoulder 25 of the box B abuts theshoulder 15 on the pin P and a predetermined amount of makeup torqueapplied thereto. When the shafts aremade up to the predetermined amountof desired torque, the cylindrical neck will be telescopically receivedwith the bore designated at 33 formed in the inner end of the box B.

Attention is now directed to the specific threaded configuration on apin end P of a shaft or hollow tubular member and a conforming threadconfiguration on a box B of a shaft or hollow tubular member. It will benoted that each thread on the threaded portion 20 of the pin P isprovided with one flank which may be designated as the stabbing flankand referred to by the numeral 35. Similarly a stabbing flank 36 isprovided on each of the threads on the threaded portion 26 of the box B.Each of the threads is provided with two flanks and on the threadedportion 20 of pin P the other flank is referred to by the number 38which is referred to as the load or pressure flank and the similar ormating thread flank on the threaded portion 26 of the box B is referredto by the numeral 40. It will be noted that the thread flanks 35 and 38on each of the threads on the threaded portion 20 of the pin P areadjacent but opposed and are joined by the root 35a of each of thethreads referred to by the numeral 41. Similarly the stabbing flank 36and the load flank 40 on the threads of box B of the threaded portion 26are adjacent but opposed and are joined by a root 41a The roots of eachof the threads on each of the threaded portions 20 and 26 are formed ona radius which is tangent to the thread flanks which the roots jointogether.

Each of the crests of each of the threads on the threaded portion 20 ofthe pin P is of a length referred to by the number 44 and each of thethread crests on the threaded portion 26 on the box B is of a lengthreferred to by the number 45.

It will be noted that when the pin p and box B are threadedly engaged ormade up the construction and arrangement of each of the threads on thethreaded portion 20 and the construction and arrangement of each of thethreads on the threaded portion 26 are such that the load flanks 38 and40 will be engaged and the stabbing flanks 35 and 36 will be in spacedrelation to its respective root when the pin and box are made up so thata continuous helical void is formed throughout the threaded portion 20on the pin P and the threaded portion 26 on the box B.

The unthreaded portion 23, as more clearly seen in FIG. 2 of thedrawings, is spaced relative to the cylindrical neck 18 formed on thepin P and extending longitudinally from the shoulder 15 to form annularvoid or space 50. Similarly the unthreaded portion 28 at the inner endof the box B is on a larger diameter than the portion 21a of the nose 21adjacent thereto, as previously mentioned.

This arrangement enables any mud, dirt, scale, particles of rock orother contamination to be extruded through the voids formed between thethreaded portions 20 and 26 and into the voids 50 and 51 at each endthereof as the joints are made up and thereby tends to reduce thetendency of the box B to split and the tendency of the pin P to breakoff caused by pressure of foreign matter between the threaded portion ofthe pin P and the threaded portion of the box B in other arrangements.

Similarly, attention is directed to the fact the stress raising contoursof the threaded arrangement are substantially reduced in that there areno sharp comers or V-shaped edges formed on the threads which make upthe threaded portion 20 on the pin P and the threaded portion 26 on thebox B.

In addition, experience with the threaded arrangement with the presentinvention indicated that the relationship of breakout torque to make uptorque remains substantially constant for the configuration embodied anddescribed herein regardless of the presence or lack of foreign matter orthe presence or lack of lubrication.

The configuration of the threaded connection of the present invention isrelated in part to the outside diameter of the shaft. In those instanceswhere an internal bore extends longitudinally of the shaft, somedimensions are determined by considering the internal diameter of thebore as well. It can be appreciated that the present invention can beapplied to shafts of any diameter and that the critical dimensions andarrangement of the threaded configuration are determined by therelationships as given hereinafter. Also, by way of example only theremay be some slight variationthat is, the same thread may be used on ashaft of 7%inches in diameter as on an 8%inch diameter shaft. Thepreferred relationships are:

thread lead =O.D. divided by about 10 pin neck length =O.D. divided byabout 7.25

thread height =O.D. divided by about 40 thread root radius =threadheight divided by about 2 thread crest length ==thread height divided byabout 2 pin overall length =O.D. multiplied by about 0.8

thread taper =(O.D.-I.D.), and this divided by about 2 angle betweenadjacent but opposed thread flanks or surfaces =from about 75 to about100 load flank angle relative to axis of shaft is from about 50 to about70 stabbing flank angle relative to axis of shaft from about 20 to about40 pitch diameter about 0.700 to about 0.800 of OD. (.800

being preferred) nose diameter about 0.625 to 0.700 of 0D. (0.675 beingpreferred) pin neck diameter about 0.750 to about 0.800 of 0D.

0.750 being preferred) Pitch diameter may be defined as the averagediameter of the rests of the threads plus the average diameter of theroots of the threads divided by about 2.

It can be appreciated that where the thread taper is referred to thatthe ID. will be zero on a solid shaft, since there is no bore extendinglongitudinally therethrough (i.e. no I.D). Similarly, where no nose 21is used, the nose diameter will be zero. By way of example the threadedarrangement for a shaft having an outer diameter (CD. in the foregoingrelationships) of about 10" when using the above critical relationshipswould be as follows:

thread lead is 10 inches divided by 10=l inch pin root length is 10inches divided by 7.25=l .38 inches thread height 10 inches divided by40 =0.250 inch thread root radius 0.250/2=0. inch thread crest length=0.250/2=0. 125 inch pin overall length 10 inches multiplied by 0.8=8inches thread taper is 10 inches 4 inches divided by two times 10 inches6 inches divided by 20 inches 0.3 inch pitch diameter 0.8 multiplied by10 inches 8 inches nose diameter 0.675 multiplied by 10 inches 6.75

inches pin neck diameter 0.750 multiplied by 10 inches 7.5

inches Attention is directed to the fact that when the pin P and the boxB are threadedly engaged as shown in FIG. 2 of the drawings, and the pinP and box B are made up to the desired torque the nose 21 will snuglyfit within the bore 33 formed in the inner end of the box B to aid inmaintaining rigidity and re sist bending moments. It can be appreciatedthat where the shaft is not provided with a bore 11a as shown in FIG. 2of the drawings then the bore 33 in which the pin 22 is telescopicallyreceived, would terminate adjacent the end 22 of the hose 21.

It will be noted that the pin neck 18 has a constant cross sectionthroughout its length which is considerable relative to the threadedportion 20 on the pin P. The combined stresses on the pin neck 18 aredistributed evenly over the length of the cylindrical neck 18 and theconstruction may withstand very large stresses, thus reducing thelikelihood of failure compared with what it would be in the absence ofthe relatively long uniform cylindrical neck 18 as embodied in thepresent invention.

When the pin and box are made up, the nose 21 fits snugly within thebore 33 of the box B and aids in preventing wobbling of the connectedshaft during operation. This close fit between the joints provides anarrangement which will transmit extremely high rotational torques incombination with extremely high compressive and tensile loads arisingfrom imposed input power, weight of the shafts connected together inaddition to forces arising from alternating stresses resulting from highreverse bending moments.

While the pin neck 18 is a critical section from the standpoint ofpossible failure due to the fact that combined stresses induced bytorque-up, or joint makeup preload, working tensile load and appliedbending moments are all additive, it can also be appreciated that theroots of all of the engaged threads on the threaded portions 20 and 26respectively are subject to tensile loads and are hence subject tofailure. However, the thread configuration of the present inventionemploys a thread root of a large radius which minimizes the likelihoodof tensile or fatigue failures in this portion of each of the threadedportions on the box B and pin P by embodying a complete and maximumradius which is tangent to both thread flanks with which it is joined ateach end.

It can be appreciated from viewing the threaded arrangement shown inFIGS. 1 and 2 of the drawings that the threaded portion 20 on the pin Preduces in diameter from the cylindrical neck 18 to the nose 21 toprovide a taper in the threaded portion 20. Similarly the threads of thethreaded portion 26 on the box B are on a larger diameter than the lastthread adjacent the unthreaded portion 28 at the inner end of the box Bso that the threaded portion 26 is also generally tapered.

By referring to FIG. 3 the diameter of the nose 21 is determined by thediameter as represented by the dotted line extending across FIG. 2 andreferred to by the numeral 60. In FIG. 3 only one half of the pin isrepresented, the center line being indicated by the line 61 so that thedistance represented by the line 63 is the nose radius.

It will be noted that the pin length is represented by the total lengthof the pin from the shoulder to the end 22 of the pin and identified bythe line 65. Similarly the length of the cylindrical pin neck 18 isrepresented at 66, the lead of the threads at 67; the width of the crestof each thread at 68; the thread root radius at 69; the thread height at70 and the taper of thethread by the line 71 which is a line in a planetangent to the crest of the threads on the pin and the box respectivelyand its angular relationship to the longitudinal axis of the shaftrepresented by the centerline 61. The angle between the load flanks andstabbing flanks is shown as being between 75 to 100, with the stabbingflank angle relative to the axis of the shaft being to 40 and with theload flank angle relative to the axis of the shaft being 50 to 70.

It will be noted that the stabbing flank is inclined more relative tothe longitudinal axis of the shaft than the load flank as more clearlyillustrated in H6. 3 of the drawings. Also, the stabbing flank of eachthread is substantially longer than the load flank of each thread sothat when the pin P and box B are initially stabbed together there is asubstantial surface contact between the stabbing flanks on the pin P andbox B.

FIG. 4 is a chart representing torque values typical for a 10 inchesouter diameter shaft or joint with the vertical axis on the leftrepresenting the makeup torque in units of thousand foot pounds and thehorizontal axis representing the breakout torque in thousand footpounds. lt will be noted that when the pin and box are clean andlubricated, for example, a predetermined makeup torque of approximately72,000 foot pounds will require a breakout torque of 30,000 foot pounds.This is represented by the line 80. The line 81 represents therelationship of makeup torque to breakout torque when the pin and boxare lubricated and dirty, and the curve 82 represents the same when thepin and box are dry and dirty, and the line 83 represents the same whenthe pin and box are dry and clean.

it will be noted that the curves or lines 80, 811, 82 and 83 present afamily of curves so that the relationship of makeup torque to breakouttorque is shown as being substantially constant regardless of thecondition of the joint. In using the present invention it is preferredthat the joint be made up to a predetermined torque initially to preventadditional makeup during use, as such condition is highly undesirable inearth boring operations. The predetermined makeup torque can be appliedin any well-known manner as the pin and box are threadedly engaged.

Also, it can be appreciated that the misalignment represented in FIG. Iof the drawings most often would occur when earth boring operations areconducted on other than in a vertical'opening; however such misalignmentmay occur as well in a vertical bore.

By referring to the chart, FIG. 4, it can be appreciated that thethreaded arrangement of the present invention gives a constantrelationship between makeup torque and breakout torque generallyregardless of the presence of foreign matter in the threads or the typeand/or amount of lubrication or lack of lubrication in the pin and boxwhen they are engaged. This is quite advantageous in that the threadedarrangement when employing the critical parameters as hereinbefore givenachieves proper and predictable breakout torque to disengage the pin andbox from each other.

Also, by applying a predetermined make up torque to connect the pin andbox together it is possible to ascertain the compressive loads andstresses in the shoulder areas of the pin and box and the offsettingtensile loads and stresses in the pin and neck so as to operate orconduct the earth boring operations within the design limits of thethreaded arrangement and shafts.

in FIG. 5, a shaft or tubular member 12 is shown wherein a pin P isprovided on each end, and in FIG. 6 the shaft 11 is shown as having abox B on each end. It is contemplated that the thread configuration onshafts 11' and 12 will have parameters similar to that previously setforth herein.

When using the arrangement of FIGS. 5 and 6, it can be appreciated thatthe drill string will be composed of a shaft 11 and then a shaft 12', sothat the pins and boxes can be threadedly engaged. Also, while theshafts are shown as being hollow, they may be solid and the nose 21' maybe eliminated as previously discussed with regard to FIG. 2. If desired,the shaft 11' may have a bore as shown, or the bore may be enlarged byremoving the material along the dotted lines E. thus saving somematerial.

F IG. 7 is a sectional view of a part of a threaded connection andillustrates that the thread size of the present invention increases asthe shaft outer diameter increases to provide a stronger thread forlarger shafts. A shaft 12 is shown as having a pin P and a box B andshaft 11 is shown engaged therewith. It

can be seen from FIG. 7 that as the outer diameter of the shaftsincrease, the thread size of the present invention also increases. Thisincreases the area of the stabbing flank and load flank to initiallyaccommodate the impact loading on the stabbing flanks as the shafts arestabbed together, and by increasing the area of the load flank inproportion to the shaft diameter, a greater load carrying area isprovided. WHAT WE CLAIM IS:

1. A thread configuration for the pin and box of shafts for connectingthe shafts together, said thread configurations having the followingcharacteristics:

a. thread lead O.D. divided by about 10;

b. pin neck length O.D. divided by about 7.25;

c. thread height =O.D. divided by about 40;

d. thread root radius thread height divided by about two;

e. thread crest length thread height divided by about two;

f. pin overall length =O.D. multiplied by about 0.8;

g. thread taper =(O.D.l.D.) and this divided by about two times O.D.;

h. angle between flanks about 75 to about i. load flank angle relativeto axis of shaft about 50 to about 70;

j. stabbing flank angle relative to axis Of shaft about 20 to about 40;

k. pitch diameter about 0.700 to about 0.800 ofdiameter;

l. nose diameter about 0.625 to about 0.700 of diameter;

m. pin neck diameter about 0.750 to about 0.800 of diameter;

n. wherein 0D. is the outer diameter of the shafts;

0. wherein thread lead is the number of threads per inch;

p. wherein pin neck length is the length of the cylindrical surface onthe pin from the end of the threads to the shoulder on the pin;

q. wherein thread height is the vertical distance from the root to thecrest of the thread;

r. wherein pin overall length is the length of the pin from saidshoulder to the end of the pin;

s. wherein ID. is the internal diameter of any bore extending throughthe shafts;

. wherein thread taper is represented by a line in a plane tangent tothe crests of the threads on the pin and box and its angularrelationship to the longitudinal axis of the shafts;

u. wherein pitch diameter is average of diameter of crest of thread andaverage diameter of root of thread divided by v. wherein the anglebetween the flanks is the angle between two adjacent, opposed surfacesof a thread;

. wherein the load flank is the surface of the thread on the pin whichengages a similar thread surface on the box when the pin and box of theshafts are made up; and

x. wherein the stabbing flank is the surface of the thread on the pinwhich is not engaged with a similar thread surface on the box when thepin and box of the shafts are made up.

A threaded connection for shafts comprising:

a. a box of at least one end of one of the shafts; b. a pin on at leastone end of another shaft, said pin and box having a conforming threadconfiguration whereby adjacent shaft ends may be connected together bythreadedly engaging the pin of one of said shafts in the box of theother shaft;

c. said pin including a shoulder projecting inwardly from the outerdiameter of the shaft;

d. a cylindrical neck extending longitudinally from said shoulder and onsmaller diameter than the outer diameter of said shaft;

e. a threaded portion on said pin and extending longitudinally from saidcylindrical neck an unthreaded cylindrical nose extending longitudinallyfrom said threaded portion; said box having an unthreaded portionadjacent its outer end which is in spaced relation to said cylindricalneck on said pin when said pin and box are made up to provide an annularspace adjacent the outer end of said box between said pin and box whenthey are made up; g. a threaded portion extending from said unthreadedportion into said box; said box having an unthreaded portion adjacentand extending longitudinally from said threaded portion in said box andbeing in spaced relation to at least a portion of said cylindrical noseon said pin when said box and pin are threadedly made up to provide anannular space adjacent the inner end of said box between said pin andbox when they are made up;

. said threaded portion on said pin and box being tapered and eachthread having two adjacent flanks, one of said flanks on said pin forcontacting a similar flank on said box when said pin and box are stabbedtogether to be made up, and the other of said flanks on said pinengaging a similar flank on said box to transmit load in said connectionwhen said pin and box are made up;

j. said flanks on said threads on said pin which engage said flanks onsaid threads on said box when said pin and box are stabbed together tobe made up being in spaced relation when said pin and box are made up toform a helical void therebetween when said pin and box are connectedtogether;

k. the crests of said threads in said pin and said box being flat andhaving a predetennined length;

. the roots of said threads in said pin and box being formed on a radiuswhich is tangent to the thread flanks which said roots join togetherwhereby said flat crests of said threads are in spaced relation to saidroots when said pin and box are made up to form a void whichcommunicates with the void formed between said stabbing flanks when saidpin and box are made up; and

m. said annular spaces adjacent the inner end and outer end of said boxcommunicating with said voids whereby contamination on said pin and boxmay be extruded thereinto as said pin and box are made up.

3. The invention of claim 2 wherein said shafts are solid.

4. The invention of claim 2 wherein said shafts are provided with aninternal bore therethrough.

5. The invention of claim 2 wherein said thread configuration on saidpin and box has the following characteristics:

a. thread lead O.D. divided by about 10;

b. pin neck length =O.D. divided by about 7.25;

c. thread height =O.D. divided by about 40;

d. thread root radius thread height divided by about 2;

e. thread crest length thread height divided by about two;

f. pin overall length =O.D. multiplied by 0.8;

g. thread taper (O.D.l.D.) divided by about two multiplied by O.D.;

h. angle between flanks about 75 to about 100;

i. load flank angle relative to axis of shaft about 50 to about 70;

j. stabbing flank angle relative to axis of shaft about 20 to about 40;and

k. wherein D. is the outer diameter of the shaft.

6. The invention of claim 1 wherein said box has an unthreadedcylindrical portion extending from said unthreaded portion next to saidthreaded portion for receiving said cylindrical nose of said pin whenpin and box are threadedly made up.

7. A thread configuration for the pin of a shaft having the followingcharacteristics:

a. thread lead O.D. divided by about 10;

b. pin neck length O.D. divided b about 7.25; c. thread height O.Ddivided by about 40;

d. thread root radius thread height divided by about two; e. threadcrest length thread height divided by about two; f. pin overall lengthO.D. multiplied by about 0.8;

g. thread taper= (O.D.l.D.) and this divided by about two times O.D.;

h. angle between flanks= about 75 to about i. load flank angle relativeto axis of shaft about 50 to about 70";

j. stabbing flank angle relative to axis of shaft about 20 to about 40;

k. pitch diameter about 0.700 to about 0.800 ofdiameter;

1. pin neck diameter about 0.750 to about 0.800 of diameter;

m. wherein 0D. is the outer diameter of the shaft;

n. wherein thread lead is the number of threads per inch;

0. wherein pin neck length is the length of the cylindrical surface onthe pin from the end of the threads to the shoulder on the pin;

p. wherein thread height is the vertical distance from the root to thecrest of the thread;

q. wherein pin overall length is the length of the pin from saidshoulder to the end of the pin;

r. wherein ID. is the internal diameter of any bore extending throughthe shaft; and

s. wherein thread taper is represented by a line in a plane tangent tothe crests of the threads on the pin and its angular relationship to thelongitudinal axis of the shaft.

8. The invention of claim 8 wherein said shaft is solid.

9. The invention of claim 8 wherein said shaft is provided with aninternal bore therethrough.

10. The invention of claim 8 wherein there is an unthreaded cylindricalnose extending from said threaded portion on said pin to the end of saidshaft.

11. A thread configuration for the box of a shaft having the followingcharacteristics:

a thread lead O.D. divided by about 10;

b. thread height O.D. divided by about 40;

c. thread root radius thread height divided by about two;

d. thread crest length thread height divided by about two;

e. thread taper =(O.D.l.D.) and this divided by about two times O.D.; 1

f. angle between flanks about 75 to about 100;

g. load flank angle relative to axis of shaft about 50 to about 70;

h. stabbing flank angle relative to axis of shaft about 20 to about 40;

i. pitch diameter about 0.700 to about 0.800 of diameter; j. whereinO.D. is the outer diameter of the shaft; k. wherein thread lead is thenumber of threads per inch; I. wherein thread height is the verticaldistance from the root to the crest of the thread; m. wherein l.D. isthe internal diameter of any bore extending through the shaft; and n.wherein thread taper is represented by a line in a plane tangent to thecrests of the threads on the box and its an gular relationship to thelongitudinal axis of the shaft. 12. The invention of claim 12 whereinsaid shaft is solid. 13. The invention of claim 12 wherein said shaft isprovided with an internal bore therethrough.

14. The invention of claim 12 wherein there is n unthreaded cylindricalnose extending from said threaded portion on said pin to the end of saidshaft.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent3,586,353 Dated June 22. 197i Inventofls) HOWARD I. LORENZ AND KEES M.VERHEUL It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

. '1 Column 1, lines 65 and 66, cancel "a of the prior art is that thethreaded".

Column 2, lines 42, 43, 47, and 63; Column 3, lines 40 and 45, change"makeup" to -makeup.

Column 4, line 6, after "15'' insert which.

Column 4, line 54, change "threaded" to thread-.

Column 5, line 37, change "indicated" to indicates-.

Column 5, line 60, after "2" insert times the O.D.-.

Column 5, line 74, change "rests" to -crests.

Column 6, line 16, b f 6" insert Column 5, line 5, change "p" to P--.

Column 6, line 30, change "hose" to nose.

Column 7, lines 24, 28, 31, 37, 41, 43, and 53, change "makeup" to-makeup. V

Column 10, line .l,vbefo re "pin" insert said.

Column 10, line 67, change "n to -an-.

Signed and sealed this hth. 4:313 1f W ch 72.

SEAL) Attest:

EDWARD ELFLETCHE? ,JF', F:-' B -1. I GOT"? "FIAT."

Attesting Officer Cummissiono f. 7mm

1. A thread configuration for the pin and box of shafts for connectingthe shafts together, said thread configurations having the followingcharacteristics: a. thread lead O.D. divided by about 10; b. pin necklength O.D. divided by about 7.25; c. thread height O.D. divided byabout 40; d. thread root radius thread height divided by about two; e.thread crest length thread height divided by about two; f. pin overalllength O.D. multiplied by about 0.8; g. thread taper (O.D.- I.D.) andthis divided by about two times O.D.; h. angle between flanks about 75*to about 100*; i. load flank angle relative to axis of shaft about 50*to about 70*; j. stabbing flank angle relative to axis of shaft about20* to about 40*; k. pitch diameter about 0.700 to about 0.800 ofdiameter; l. nose diameter about 0.625 to about 0.700 of diameter; m.pin neck diameter about 0.750 to about 0.800 of diameter; n. whereinO.D. is the outer diameter of the shafts; o. wherein thread lead is thenumber of threads per inch; p. wherein pin neck length is the length ofthe cylindrical surface on the pin from the end of the threads to theshoulder on the pin; q. wherein thread height is the vertical distancefrom the root to the crest of the thread; r. wherein pin overall lengthis the length of the pin from said shoulder to the end of the pin; s.wherein I.D. is the internal diameter of any bore extending through theshafts; t. wherein thread taper is represented by a line in a planetangent to the crests of the threads on the pin and box and its angularrelationship to the longitudinal axis of the shafts; u. wherein pitchdiameter is average of diameter of crest of thread and average diameterof root of thread divided by 2; v. wherein the angle between the flanksis the angle between two adjacent, opposed surfaces of a thread; w.wherein the load flank is the surface of the thread on the pin whichengages a similar thread surface on the box when the pin and box of theshafts are made up; and x. wherein the stabbing flank is the surface ofthe thread on the pin which is not engaged with a similar thread surfaceon the box when the pin and box of the shafts are made up.
 2. A threadedconnection for shafts comprising: a. a box of at least one end of one ofthe shafts; b. a pin on at least one end of another shaft, said pin andbox having a conforming thread configuration whereby adjacent shaft endsmay be connected together by threadedly engaging the pin of one of saidshafts in the box of the other shaft; c. said pin including a shoulderprojecting inwardly from the outer diameter of the shaft; d. acylindrical neck extending longitudinally from said shoulder and onsmaller diameter than the outer diameter of said shaft; e. a threadedportion on said pin and extending longitudinally from said cylindricalneck an unthreaded cylindrical nose extending longitudinally from saidthreaded portion; f. said box having an unthreaded portion adjacent itsouter end which is in spaced relation to said cylindrical neck on saidpin when said pin and box are made up to provide an annular spaceadjacent the outer end of said box between said pin and box when theyare made up; g. a threaded portion extending from said unthreadedportion into said box; h. said box having an unthreaded portion adjacentand extending longitudinally from said threaded portion in said box andbeing in spaced relation to at least a portion of said cylindrical noseon said pin when said box and pin are threadedly made up to provide anannular space adjacent the inner end of said box between said pin andbox when they are made up; i. said threaded portion on said pin and boxbeing tapered and each thread having two adjacent flanks, one of saidflanks on said Pin for contacting a similar flank on said box when saidpin and box are stabbed together to be made up, and the other of saidflanks on said pin engaging a similar flank on said box to transmit loadin said connection when said pin and box are made up; j. said flanks onsaid threads on said pin which engage said flanks on said threads onsaid box when said pin and box are stabbed together to be made up beingin spaced relation when said pin and box are made up to form a helicalvoid therebetween when said pin and box are connected together; k. thecrests of said threads in said pin and said box being flat and having apredetermined length; l. the roots of said threads in said pin and boxbeing formed on a radius which is tangent to the thread flanks whichsaid roots join together whereby said flat crests of said threads are inspaced relation to said roots when said pin and box are made up to forma void which communicates with the void formed between said stabbingflanks when said pin and box are made up; and m. said annular spacesadjacent the inner end and outer end of said box communicating with saidvoids whereby contamination on said pin and box may be extrudedthereinto as said pin and box are made up.
 3. The invention of claim 2wherein said shafts are solid.
 4. The invention of claim 2 wherein saidshafts are provided with an internal bore therethrough.
 5. The inventionof claim 2 wherein said thread configuration on said pin and box has thefollowing characteristics: a. thread lead O.D. divided by about 10; b.pin neck length O.D. divided by about 7.25; c. thread height O.D.divided by about 40; d. thread root radius thread height divided byabout 2; e. thread crest length thread height divided by about two; f.pin overall length O.D. multiplied by 0.8; g. thread taper (O.D.- I.D.)divided by about two multiplied by O.D.; h. angle between flanks about75* to about 100*; i. load flank angle relative to axis of shaft about50* to about 70*; j. stabbing flank angle relative to axis of shaftabout 20* to about 40*; and k. wherein O.D. is the outer diameter of theshaft.
 6. The invention of claim 1 wherein said box has an unthreadedcylindrical portion extending from said unthreaded portion next to saidthreaded portion for receiving said cylindrical nose of said pin whenpin and box are threadedly made up.
 7. A thread configuration for thepin of a shaft having the following characteristics: a. thread lead O.D.divided by about 10; b. pin neck length O.D. divided by about 7.25; c.thread height O.D divided by about 40; d. thread root radius threadheight divided by about two; e. thread crest length thread heightdivided by about two; f. pin overall length O.D. multiplied by about0.8; g. thread taper (O.D.- I.D.) and this divided by about two timesO.D.; h. angle between flanks about 75* to about 100*; i. load flankangle relative to axis of shaft about 50* to about 70*; j. stabbingflank angle relative to axis of shaft about 20* to about 40*; k. pitchdiameter about 0.700 to about 0.800 of diameter; l. pin neck diameterabout 0.750 to about 0.800 of diameter; m. wherein O.D. is the outerdiameter of the shaft; n. wherein thread lead is the number of threadsper inch; o. wherein pin neck length is the length of the cylindricalsurface on the pin from the end of the threads to the shoulder on thepin; p. wherein thread height is the vertical distance from the root tothe crest of the thread; q. wherein pin overall length is the length ofthe pin from said shoulder to the end of the pin; r. wherein I.D. is theinternal diameter of any bore extending through the shaft; and s.wherein thread taper is represented by a line in a plane tangent to thecrests of the threads on the pin and its angular relationship to thelongitudinal axis of the shaft.
 8. The invention of claim 8 wherein saidshaft is solid.
 9. The invention of claim 8 wherein said shaft isprovided with an internal bore therethrough.
 10. The invention of claim8 wherein there is an unthreaded cylindrical nose extending from saidthreaded portion on said pin to the end of said shaft.
 11. A threadconfiguration for the box of a shaft having the followingcharacteristics: a thread lead O.D. divided by about 10; b. threadheight O.D. divided by about 40; c. thread root radius thread heightdivided by about two; d. thread crest length thread height divided byabout two; e. thread taper (O.D.- I.D.) and this divided by about twotimes O.D.; f. angle between flanks about 75* to about 100*; g. loadflank angle relative to axis of shaft about 50* to about 70*; h.stabbing flank angle relative to axis of shaft about 20* to about 40*;i. pitch diameter about 0.700 to about 0.800 of diameter; j. whereinO.D. is the outer diameter of the shaft; k. wherein thread lead is thenumber of threads per inch; l. wherein thread height is the verticaldistance from the root to the crest of the thread; m. wherein I.D. isthe internal diameter of any bore extending through the shaft; and n.wherein thread taper is represented by a line in a plane tangent to thecrests of the threads on the box and its angular relationship to thelongitudinal axis of the shaft.
 12. The invention of claim 12 whereinsaid shaft is solid.
 13. The invention of claim 12 wherein said shaft isprovided with an internal bore therethrough.
 14. The invention of claim12 wherein there is n unthreaded cylindrical nose extending from saidthreaded portion on said pin to the end of said shaft.